Supporting a platform

I'm building a small platform that is made of wood. It measures 40" x 12". It's also 1" thick.

I have 4 hollow aluminum pillars that will support it. They are each 8" high and 2" in diameter.

What is the optimal position for each pillar to be fixed relative to the edge of the platform? I would like to have the right balance of stability while minimizing potential bowing of the wood. It's safe to assume all additional weight will be evenly distributed.

Staff: Mentor

Welcome to PF!

Is this a homework assignment, if so then you need to use the homework template and show what you know and what you've done to solve the problem and where you're stuck.

as a first cut, it seems from symmetry that you need to place the four legs somewhere symmetrically along the two diagonals drawn on the rectangular platform. Placing them as far apart as possible is best for stability and placing them as close to the center is best for sagging in the middle.

If this is a personal project and you're worried about sagging then it would be best to provide beam support underneath the platform like say a 2x2 or two 2x2's nailed to the platform running the 40" length and placing the legs close to the corners.

Staff: Mentor

It's kinda like a free-standing shelf to be placed on a desk, so the user can periodically choose to convert their sitting workstation to a 'standing' workstation. So it will support a keyboard, mouse, maybe a coffee. Also, regular weight from resting palms.

Staff: Mentor

Cool, I was thinking of doing that recently. People at work have been getting VariDesks but when I asked they said we're out of money and so I started designing an approximation. I had 18" legs because my desk is slightly lower I tried to match the ergonomics of the VariDesk. I wound up not building it because I figured the VariDesk was that much better especially with the option to use it standing or sitting.

In any event, I think you'll be disappointed if you don't put in supports as it will surely sag no matter how much weight and aesthetically you'll hate it. You could use a right angled bar across the front and back to reduce the sag (it will provide a nice edge too) and place the legs and inch or two in from the corners. But I'd test a mockup of it first to see how it works.

Remember you only have 12" width and you're going to put a top heavy monitor on it so you want the legs as far apart as possible for the best stability.

It's kinda like a free-standing shelf to be placed on a desk, so the user can periodically choose to convert their sitting workstation to a 'standing' workstation. So it will support a keyboard, mouse, maybe a coffee. Also, regular weight from resting palms.

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For this small weight (>> 100lbs) with a 40x12" 1" wooden board sagging is not really an issue unless the wood is not dry or for some reason you choose not to cover it with PU lacquer or similar (as the right coating improves on the material properties like a composite).

As leg position is somewhat important you can choose to put the legs close to the long side and 8" from the short side. Although there is always the issue of leaning on the edge which can topple the bench. One option is a trapezoidal placement with the front legs far apart and the back legs closer to improve the sagging "issue". Thus you will have to lean on the back corner to topple the bench over.